The present invention relates to an improved device for application to metal material extruding press assemblies.
The inventive device allows a quick replacement of a heel element and/or a slot tie-rod element in said press assemblies, which elements must be replaced as they are worn.
As it is known, metal extruding press assemblies are used for extruding metal billets at an extruding temperature of about 400° C., through press pistons applying a high pressure on a heel element pushing the billet into an extruded die.
The extruding operations are performed in a quick operating succession and thereby the press operating members are greatly stressed by thermal and mechanical efforts; accordingly the heel element quickly wears and must be necessarily replaced after a set number of extruding operations, usually after 20,000-40,000 extruding operations which, as stated, are performed in a quick operating succession.
It is moreover known that metal material extruding press assemblies have a high cost, thereby they are operated for 24 hours a day, without interruptions, to amortize their cost.
Up to now, the heel element replacement operations were very difficult and required long replacement time with the press assembly not operating.
Thus, the replacement of metal material extruding press assembly heel elements has been considered a very delicate operation so far, both with respect to the press operator safety standpoint and to an optimizing of the required press maintenance or servicing operations, which maintenance operations are very difficult due to the following reasons:
a) the temperature of the heel element to be removed and that of the replacement one is of at least 400° C.;
b) the weight of the heel element depends on the press assembly size and is of several dozens of kilograms, thereby the heel element must be disassembled and assembled by an auxiliary lifting equipment comprising a tackle or a idle roller lifting device.
Moreover, it is not possible to access the press assembly, because of the dangerous press driven elements.
As it is moreover known, the heel element is usually clamped to a large size threaded tie-rod having a diameter from about 40 mm to about 100 mm for large press assemblies.
Thus, it is very difficult to turn the heel element to screw on said heel to the press punch.
For example, with a threaded tie-rod having a diameter of 90 mm, pitch 3, a length of 100 mm, it is necessary to perform about 33 rotary movements (100/3) to screw off the heel element being replaced and a corresponding number of rotary movements to screw on the replacement heel element, thereby it is very difficult to clamp the heel element to its threaded tie-rod by simple clamping operations.
In fact, it is very difficult to lock, with a required locking force, a round cross section heel of a weight of several dozens of kilograms, and including a threaded portion, thereby it is necessary to use movable hammer and sectorized torque wrench assemblies.
Moreover, no dynamometric or hydraulic torque wrench assemblies for facilitating said clamping operations exist at present, thereby the clamping force is applied in a very approximated manner.
Thus, during the replacement operation, the heel element may be accidentally detached and damage the press assembly.
Other heel elements are attached by a bayonet attachment, of a Castol type or the like, which attachment system, while having some operating advantages, has also great disadvantages.
An advantage is that, for attaching the heel element, it is necessary to turn it through only 45°.
A disadvantage is that it is not possible to lock the replacement heel element with a zero clearance, since an operating clearance between the bayonet assembly head and the related seat is always present, which clearance is negatively affected by thermally changing conditions always present in such a press assembly.
Another factor negatively affecting this attachment operation is a clearance increase or growth due to wear and frequent pulling and releasing operating cycles.
The inventive device facilitates and speeds up the heel element replacement operations, independently of the fact that either the replacement heel element is brought manually to a desired position, by a tackle, or is brought to said target position by a further automatically operating handling device.
In the inventive device, the replacement heel is brought to said target position, i.e. in front of the press punch, and is threaded on the rod up to achieve a mechanical abutment.
Then the slotted tire-rod is turned through 30°, while controlling and limiting the tie-rod torque.
If a precise target position is not achieved, then the tie-rod does not further turn, thereby a related end of stroke element does not arrive at said target position, causing the press to provide an alarm signal preventing any further operating steps.
As the control end of stroke or limit assembly arrives at the target position, the inventive device is automatically switched to a following operating step, that is the tie-rod pulling through a hydraulic cylinder.
A reverse operation will be performed when the heel element must be disassembled.
On the other hand, if the tie-rod must be disassembled, then it is necessary to perform a rotary 45° movement with respect to a zero position, to axially disengage the tie-rod and unthread it from the press punch.
For assembling the tie-rod, an opposite operation must be carried out, by performing a 45° rotary movement of the rod with respect to the zero position, to disengage it from the punch.
Thus, the system has three rotary positions all controlled by the end of stroke or limit assembly, which positions are:
1. a locked heel element position;
2. an unlocked heel element position;
3. an unlocked tie-rod position.